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JXC 5Aphy 2023-24 > Booklet 2A - Particles (Factual) > Flashcards

Booklet 2A - Particles (Factual) Flashcards

1
Q

What is the Standard Model?

A

The Standard Model explains what the basic building blocks of matter are and how they interact, governed by four fundamental forces.

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2
Q

Where does the evidence for the existence of quarks come from?

A

High-energy collisions between electrons and nucleons, carried out in particle accelerators.

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3
Q

What is a fundamental particle?

A

A fundamental particle is one that cannot be broken down into any sub particles.

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4
Q

What is a Fermion?

A

It is a fundamental matter particle.

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5
Q

What are the two types of Fermions?

A

Quark

and

Lepton

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6
Q

What are the names of the 6 types of Quarks?

A
  1. Up
  2. Down
  3. Charm
  4. Strange
  5. Top
  6. Bottom
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7
Q

What are the names of the 6 types of Leptons?

A
  1. Electron
  2. (Electron) neutrino
  3. Muon
  4. Muon neutrino
  5. Tau
  6. Tau Neutrino
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8
Q

What is meant by a Hadron?

A

Particles made from quarks

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9
Q

What are the two types of Hadrons?

A

Baryon

and

Meson

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10
Q

What is meant by a Baryon?

A

Baryons are made from 3 quarks

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11
Q

What is meant by a Meson?

A

Mesons are made from 2 quarks.

They always consist of a quark and an antiquark pair.

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12
Q

Give an example of a Baryon.

A

Proton

Neutron

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13
Q

How does an antimatter particle compare with a matter particle?

A

Antimatter particle has identical properties to the matter particle but equal and opposite charge.

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14
Q

What evidence is there for antimatter?

A

Production of energy in the annihilation of particles (e.g. positrons and electrons used in PET scanners)

Positrons discovered occurring naturally in cosmic rays.

Anti-neutrinos produced as part of Beta Decay.

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15
Q

Name the force-mediating particles (Bosons).

A

Photons
W and Z Bosons
Gluons

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16
Q

What force is mediated by a photon?

A

Electromagnetic Force

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17
Q

What force is mediated by W and Z bosons?

A

Weak force

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18
Q

What force is mediated by a Gluon?

A

Strong force

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19
Q

What is the force-mediating particle for the Weak Nuclear Force?

A

W and Z bosons.

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20
Q

What is the force-mediating particle for the Strong Nuclear Force?

A

The Gluon.

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21
Q

What is the force-mediating particle for the Electromagnetic Force?

A

The Photon

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22
Q

A proton is made up of two up quarks and a down quark. The up quarks are both positively charged. Why does the proton not get torn apart?

A

The attractive Strong Nuclear force between the quarks is greater than the repulsive Electromagnetic force between them.

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23
Q

Describe beta (minus) decay?

A

Beta (minus) decay is when a neutron decays into a proton releasing an electron and an antineutrino.

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24
Q

What did beta decay provide the first evidence for?

A

The existence of neutrinos/antineutrinos.

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25
Q

Why were neutrinos suggested as an extra particle produced as a result of beta decay?

A

When beta decay occurs momentum and energy should be conserved. This didn’t appear to be true when the proton and beta particle were considered on their own. There had to be another particle that accounted for the rest of the energy/momentum.

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26
Q

In physics what is meant by a field?

A

It is the region where an object experiences a force.

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27
Q

What type of field will a stationary charge create?

A

An electric field

28
Q

What is the effect of an electric field on a charged particle?

A

A charged particle will experience a force in an electric field (causing an acceleration if it is free to move).

29
Q

Draw the electric field around a positive charge.

A

Field lines away from the positive charge.

30
Q

Draw the electric field around a negative charge.

A

Field lines towards negatively charged particle.

31
Q

Draw the electric field between a positive charge and a negative charge.

A

Field lines run from positive towards negative.

32
Q

Draw the field lines between two positive charges.

A

Field lines run away from the positive charges. No field lines between them.

33
Q

Draw the field lines between two negative charges.

A

The field lines run towards the negative charges but no field lines between them.

34
Q

Draw the field lines between parallel plates.

A

Field lines run from positive to negative plates and are parallel and evenly spaced.

(Curved lines at edges are not always required or included but are safer to leave in)

35
Q

What is meant by a uniform field?

A

A field which applies the same force per unit charge at all points.

(e.g. between parallel plates)

36
Q

Define voltage (potential difference).

A

Voltage (potential difference) is the work done moving a unit of charge between two points.

37
Q

Define a voltage (potential difference) of 1 Volt?

A

There is a voltage (potential difference) of 1 Volt between two points if 1 joule of energy is required to move 1 coulomb of charge between the two points.

38
Q

What type of field will a moving charge produce?

A

A Magnetic field

39
Q

What will a moving charge experience in a magnetic field?

A

A force

40
Q

What do the fingers represent in the right hand rule?

A
  1. First Finger - Field (Magnetic field)
  2. SECond finger - Electron Current (Opposite for Positive Charges)
  3. THumb - Thrust (Movement)
41
Q

What represents a magnetic field coming ‘out of the page’?

A

A dot

42
Q

What represents a magnetic field going ‘into the page’?

A

A cross

43
Q

Explain how a particle accelerator works.

A
  1. Acceleration of charged particles - use an electric field to accelerate them in a straight line.
  2. Deflection of charged particles - magnetic fields are used to change the direction of the moving charged particles.
  3. Collision of charged particles - against a fixed target or between two beams of particles.
44
Q

Does a particle accelerator use a.c. or d.c. to create the electric field?

Explain why.

A

a.c.

This is because the electric field must change direction regularly to keep the accelerating field in the correct direction for the particles motion.

45
Q

Describe the Rutherford Model of the atom.

A

The protons and neutrons are in the nucleus (centre) of the atom.

The electrons orbit the nucleus.

The nucleus is tiny compared to the atom (The radius of the nucleus is approx. 1/10,000th of the radius of the atom). Most of the atom is empty space between the orbits of the electrons.

46
Q

Explain the evidence for the Rutherford Model of the atom.

A

High Energy Alpha particles were fired at thin gold foil (a few hundred atoms wide) .

Most Alpha particles went straight through, showing that the atom was mostly empty space.

A very small proportion of Alpha particles were deflected slightly as they passed close to the nucleus. This showed that the nucleus was very small in size compared to the atom as a whole.

A tiny proportion were deflected back towards the Alpha source. This could only happen if they had encountered something positive and relatively heavy in a head on collision. Hence the nucleus was where the positive charge and the mass of the atom was concentrated.

47
Q

What information do you get from a chemical symbol, such as the one shown below?

A

Top number = Mass Number = combined number of protons and neutrons in the nucleus. e.g. 4 combined protons and neutrons.

Bottom Number = Atomic Number = number of protons in the nucleus. e.g. 2 protons

The letters are the chemical symbol which can be found on the periodic table.

48
Q

Describe the process of alpha emission including the effect on the mass number and the atomic number.

A

When an alpha particle (two protons and two neutrons) is emitted.

Mass Number - decreases by 4

(the product mass number + the mass number of a helium nucleus = mass number of the original unstable nucleus)

Atomic Number - decreases by 2

(the product atomic number + the atomic number of a helium nucleus = atomic number of the original unstable nucleus)

49
Q

Describe the process of beta emission including the effect on the mass number and the atomic number?

A

A neutron decays into a proton and a W- boson is emitted from the nucleus.

The W- boson decays into an electron and an antineutrino.

The mass number of the product remains the same and the atomic number increases by one.

50
Q

In the equation E = mc2 , what does the m stand for?

A

The difference in mass of the particles before the fission/fusion reaction and the mass after. This mass is converted into energy.

51
Q

What is meant by fission?

A

Fission is when a nucleus of a large mass number splits into two or more nuclei of smaller mass numbers.

52
Q

What is meant by fusion?

A

Fusion is when two small mass number nuclei combine to form a nucleus of a larger mass number.

53
Q

Give one advantage of producing electricity by nuclear fusion.

A
  • Abundant fuel supply (Deuterium can be extracted from sea water)
  • Safe (Small amounts of fuel, if reaction is unchecked it results in it stopping)
  • Clean (No combustion so no air pollution)
  • Less nuclear waste (waste is not high level weapons grade, needs stored for about 100 years)
  • Efficient (1kg fusion fuel gives same energy as 10 million kg of fossil fuels)
54
Q

What 2 conditions are required for nuclear fusion?

A
  • High Temperatures
  • High Pressure
55
Q

In a fusion reactor why are the high temperatures required a problem?

A

A high temperature is required to give the hydrogen atoms enough energy to overcome the electrical repulsion between the protons. Such a high temperature removes the electrons from the Hydrogen, turning it into a plasma. This is difficult to contain as all materials would vaporise at this temperature.

56
Q

Containment and cooling are issues associated with a nuclear fusion reactor. Why?

A

Temperature of the reaction is so high most materials will vaporise. So a magnetic field can be used to suspend the plasma away from the sides of the container.

This requires strong magnetic fields produced by superconducting coils. These only work at very low temperatures so need good cooling systems.

57
Q

What is the photoelectric effect?

A

The photoelectric effect is the removal of electrons from a metal surface by electromagnetic radiation.

58
Q

Under what conditions will a gold leaf electroscope be discharged using the photoelectric effect?

A
  • It must be negatively charged
  • It must have a zinc plate
  • Ultraviolet light of a high enough frequency must be shone on the plate
59
Q

Why does the photoelectric effect give evidence for particle-model of light?

A
  • Photoelectric effect cannot be explained if light is thought of as a wave or any light would cause photoemission if it shone on the surface long enough to deliver enough energy to the electrons.
  • If light is considered as small packets of energy called photons then the photoelectric effect can be explained.
60
Q

What does the energy of a photon depend on?

A

The energy of a photon is proportional to its frequency

61
Q

What can you say about how photons interact with electrons in the photoelectric effect?

A
  • An electron can only absorb the energy from one photon
  • The electron absorbs all the energy from the photon.
62
Q

What is the Work Function?

A

The minimum photon energy required to eject an electron from a metal surface.

63
Q

What is the threshold frequency?

A

The minimum frequency of light required for photoemission (to eject an electron from a metal surface).

64
Q

Why does light require a frequency above the threshold frequency to eject electrons from the surface of materials?

A

Light consists of photons whose energy is proportional to their frequency. Only if the frequency is high enough (above the threshold frequency) will a single photon have energy greater than the minimum energy required to eject an electron from the surface (the work function).

65
Q

If an incident photon has energy greater than the work function, what happens to the rest of the photon’s energy?

A

The electron that is ejected carries the rest of the energy in the form of kinetic energy.

66
Q

In the photoelectric effect, if the frequency of the incident radiation is increased what happens?

A

The electrons ejected will have more kinetic energy, if the frequency is greater than the threshold frequency.

67
Q

In the photoelectric effect, if the irradiance of the incident radiation is increased what will happen?

A
  • No electrons will be ejected if the frequency of the incident radiation is below the threshold frequency.
  • If the frequency is above the threshold frequency then more electrons will be ejected from the surface.

JXC 5Aphy 2023-24 (16 decks)

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